In a conventional vehicle comprising a system in which engine speed is shifted through an automatic transmission and is transmitted to wheels of a vehicle, to control most suitably a time for a gear shift, an operation force for giving a friction part is controlled according to a driving condition.
In case where the operation force for giving the friction part is high, during the shift time large unpleasant shift shock is given to crews. On the other hand, in case where the operation force for giving the friction part is low, the shift time goes too far and a service life of the friction part is shortened and further the above slow-footed sense during the shift gives the unpleasant feeling against the crews.
As a prior art technique relating to the above, according to a throttle valve opening value and vehicle speed etc., an operation force for operating a clutch related to the shift and a friction part of a brake is determined from aspects of an empirical knowledge or an experimental result and then the operation force is controlled.
Further, for example, as described in Japanese patent laid-open publication No. 72,099/1992, an operation pressure is determined from an aspect of an empirical knowledge or an experimental result using engine speed and an engine torque.
Further, for example, as described in Japanese patent laid-open publication No. 139,619/1995, from a rotation angular acceleration during a shift time, a control hydraulic pressure of an inertia component and a control hydraulic pressure of an input torque component have been requested and from a sum of the above two control hydraulic pressures an actual control hydraulic pressure for the clutch has been requested.
As stated in above, in case where the operation pressure is determined in accordance with an engine load, for example, every driving condition of an economy mode and a power mode etc. each, it is necessary to prepare a data table for the operation pressure, therefore many processing for a development design requires.
Further, as shown in Japanese patent laid-open publication No. 72,099/1992, in a method where an operation pressure is determined in accordance with an engine speed and an engine torque, a discrepancy occurs between a calculation value of an input rotation speed and an actual value in the torque converter and also a discrepancy occurs between a calculation value and an actual value in the torque according to an amplified toque.
Further, since the above discrepancies varies according to fluctuations of road gradients and vehicle weight, there is a problem in which a stable shift time and a stable shift control can not obtain.
For the above stated reasons, it is necessary to determine proportional coefficients of the engine speed and the engine torque according to the empirical knowledge every shift time each and further many data calibration processing require.
Further, as shown in Japanese patent laid-open publication No. 139,619/1995, in case where the hydraulic pressure of the clutch is requested to establish by dividing the inertia component and the input torque component, there may invite a problem about an increase in a data calibration processing number and an increase in a calculation processing step number.